This Standard specifies the physical and magnetic characteristics of a 12,7 mm wide, 18-track magnetic tape cartridge, to enable interchangeability of such cartridges. It also specifies the quality of the recorded signals, the format and the recording method, thus allowing, together with Standard
ECMA-13 for File Structure and Labelling of Magnetic Tapes, full data interchange by means of such magnetic tape cartridges.

The cartridge and recording method are identical with those described in Standard
ECMA-120. This Standard specifies extensions to the transformation of data before it is formatted as in Standard
ECMA-120.

These extensions:

specify a method for increasing the utilization of the tape by combining smaller blocks of data into extended blocks;

specify a method for identifying whether the recorded data has been processed and, if it has been processed, the algorithm used for processing;

specify a method for including recorded data blocks conforming to this Standard and recorded data blocks conforming to Standard ECMA-120 on the same tape.